1. Field of the Invention
This invention relates to record playing apparatus, and, more particularly, to apparatus for adjusting and displaying the stylus pressure exerted on a record disc by a stylus carried by a tone arm in a record playing device while the information which is recorded on the record disc is being reproduced.
2. Description of the Prior Art
In most record players, such as phonograph record players wherein sound information is reproduced by a stylus which tracks pre-recorded sound grooves, a stylus pressure-adjustment mechanism is provided to enable the user to adjust the pressure which is exerted on the record disc by the stylus. While stylus pressure must be sufficient to keep the stylus in the groove which is tracked, it must not be so great as to limit free movement and reduce the longevity of the stylus. Generally, stylus pressure is set and adjusted by a weight coupled to the rear end of the tone arm, that is, the end which is remote from the stylus, and the stylus pressure setting is indicated by direct mechanical measurement, that is, by a scale proximate the weight. As the precise position of the weight along the tone arm is adjusted, the stylus pressure is changed. A significant disadvantage in record playing devices of this kind, however, is that actual stylus pressure can not be readily ascertained or adjusted while a reproducing operation is in process, that is, while the stylus is in contact with the record disc. Rather, the reproducing operation must be interrupted and then, while the record playing device is in its quiescent condition, the actual stylus pressure can be changed. It has been proposed to move the tone arm of a recording playing device in the vertical direction by a vertical drive motor. In such a record playing device, selective energization of the vertical drive motor results in lowering the tone arm onto the surface of the record disc in order to initiate a reproducing operation, and lifting the tone arm at the completion of such a reproducing operation. That is, a current flowing through the vertical drive motor acts to control the vertical movement of the tone arm.